This invention relates to an engine control system for controlling an engine system other than the ignition system and in particular to an engine valve control system such as the exhaust control valve of a two cycle engine.
The aforenoted co-pending application disclosed a very simple but highly effective way of determining engine load and controlling an engine ignition system in response to the determined load to improve engine operation. That method and apparatus, because of its simplicity, permits incorporation in relatively small and low production volume engines as used in motorcycles, motor scooters and like engine applications.
In addition to the ignition system, the inventors have realized that there are a number of other engine control systems that are controlled by engine load and these systems generally measure engine load form operator demand, generally determined from the position of the engine throttle control. For example in two cycle engines it is common to employ an exhaust timing controller. These comprise a valve that is effective to change the exhaust timing at the exhaust port and hence the compression ratio in response to the engine revolution and load (see for example JP-A-S54-158514). Conventionally the conventional exhaust timing controller detects the throttle opening in response to the engine rotational speed and the engine load then calculates the valve opening of the exhaust control valve based on the detected engine rotational speed and throttle opening to operate a servomotor which in turn operates the exhaust control valve.
The use of a throttle opening sensor is used in the conventional exhaust timing controller and other engine control systems other than the ignition system to detect the throttle opening results in an increased number of components and a complicated control system. This obviously increases the vehicle cost. In addition small vehicles, in particular, have a layout problem in the position of the various components particularly the throttle position sensor due to the limited space around the engine.
Therefore it is the principle object of the present invention to provide an engine system controller that calculates the engine load without a throttle position sensor.
In addition most engines already have shaft position sensors that detect the angular position of the engine crankshaft for ignition control.
It is therefore another object of the invention to utilize the output of the ignition timing sensor to determine engine load for controlling an engine system other than the ignition system.